Foliar moisture content variations in four coniferous tree species of central Alberta

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Abstract
Trends of foliar moisture content variations were determined for jack pine (Pinus banksiana Lamb.), black spruce (Picea mariana (Mill.) B.S.P.), white spruce (Picea glauca (Moench) Voss), and balsam fir (Abies balsamea (L.) Mill.) in central Alberta. New and old tree foliage was periodically sampled between early March and mid-September during 2 consecutive years. The seasonally recurring variations in foliar moisture contents were characterized by (i) early spring declines of moisture in the old foliage, (ii) flushing of new foliage at high bud moisture contents when the contents in the old foliage were low, and (iii) summer recoveries of moisture in the old foliage and simultaneous decreases of moisture in the new foliage until both eventually converged toward comparable moisture contents. The cumulative effects of temperature, in terms of degree days above 6.degree. C, were reflected in timing of the declines and the recoveries of moisture in the old foliage. These results may be applied in rating the crowning potential of local forest fires.